1. Field of the Invention
Embodiments of the present invention generally relate to a tunnelling magnetoresistive (TMR) reader and a method for its manufacture.
2. Description of the Related Art
TMR readers are used in hard disk drives to read bits of data from the hard disk drive. An example of a TMR reader is shown in FIG. 1. The TMR reader 100 includes a first shield layer 102 and a sensor structure including a pinned magnetic layer 104, a barrier layer 106, a free magnetic layer 108 and a capping layer 110. The TMR reader 100 also includes an insulating layer 112, a hard bias layer 114, a hard bias capping layer 116, a top lead layer 118, and the second shield layer 120.
The capping layer 110 is used to protect the free magnetic layer 108 during later processing steps. In order to adequately protect the free magnetic layer 108, the capping layer 110 may have a thickness of between about 4 nm and about 8 nm. The top lead layer 118 is present on both the sensor structure and the hard bias capping layer 116 to provide magnetic separation between the hard bias layer 114 and the second shield layer 120. Both the capping layer 110 and the top lead layer 118 are non-magnetic.
One major limitation of the TMR reader 100 is the difficulty in scaling down the magnetic read gap (RG) dimension, which is the distance between the first shield layer 102 and the second shield layer 120. Sufficient thickness of the top lead layer 118 is needed to provide the magnetic separation between the hard bias layer 114 and the second shield layer 120. Additionally the capping layer 110 needs to be sufficiently thick to protect the free magnetic layer 108 from damage during further processing. Both the thickness of the capping layer 110 and the thickness of the top lead layer 118 combine to limit the distance from the free magnetic layer 108 to the second shield layer 120 and in turn, limit the TMR magnetic RG scaling down.